1. Field of the Invention
The present invention relates to oil well drilling tools and apparatuses. More particularly, the present invention relates to an apparatus for retrieving the wear bushing from around the interior of the well head and casing, including a sub-unit for mounting there onto the drill string.
2. General Background
Wear sleeves or wear bushings, as they are called, are utilized during oil and gas well drilling and other operations on wells to protect against excessive wear, in particular, the wear bushings prevent wear to seal areas of casing heads and other well head elements, including the joint of the housing and the initial length of pipe or casing to which it is secured.
In U.S. Pat. No. 3,747,914 issued to Slack, the wear sleeve is equipped with an interior bore smaller in diameter than the width of the bit so that the sleeve may be somewhat loosely incorporated on the drill string, resting on the drill bit and lowered to its position in order to operate as a drill string is run into the hole and retrieved from the bit as the bit is withdrawn following the drilling process. However, often times it may be desirable to retrieve the wear sleeve or bushing without the use of the bit. For example, when the drill pipe is lodged, the pipe may be backed off above the drill bit and withdrawn from the hole leaving the drill collar and bit itself down in the hole.
In order to retrieve the drill collars and bit, it is necessary to wash over with a wash over string larger in inside diameter than the outside diameter of the drill collar and equal to that of the bit itself. Due to the size, the aforementioned equipment will not go through a normal wear sleeve, and it becomes necessary to remove the wear sleeve or bushing.
One of the methods utilized in the present state of the art, as exhibited in U.S. Pat. No. 3,489,214 issued to Phipps, et al, the removal of the wear sleeve or bushing in those instances when removal of the bit is undesirable or impossible as taught. One would use a wear sleeve or bushing section providing with what is called a J-slot and a retriever body having outwardly protruding dowels or the like for engaging the J-slot. The dowels or the like would protrude around the entire radias of the retriever body. This retriever is incorporated in the drill string with the usual pin and box threaded upper and lower ends. In the preferred embodiment, the tool is a body having a longitudinally through bore large enough to pass over the upset end of a pipe, a plurality of segmental split sleeves slidably into the bore of the end facing away from the pipe upset end; means defining a lineable opening radially through the body in splits sleeves; the split sleeves having lower end surfaces adapted to seat on the rear of the pipe upset end; screws threadably advancable in said openings, partly through the body, and to the respective sleeves and into engaging with the exterior of the pipe to secure the two together and prevent its rotation with respect to the pipe. Protruding means such as radial projecting pins are provided on the tool for engaging a cooperating means on the wear sleeve or similar element.
One of the short comings of this particular apparatus as taught in U.S. Pat. No. 3,489,241 is the fact that the retriever body must be secured in rigid engagement with the exterior of the pipe so that it will not rotate with respect to the pipe. This shortcoming shall be discussed in the latter sections of this application.